Magnetic material



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COAThe'G 0R PUST'C May 15, 1928.

Cross Reference 1,669,642 J. w. ANDREWS MAGNETIC MATERIAL Filed April 17,1926

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a of the, whole. The metal particles are treat-- mary insulating coating, after which the obtaine Patented May 15, I928.

i UNITED S AT S A96, 1,669,642 PATENT OFFICE.

JOHN 'WENDELL ANDREWS, OF CHICAGO, ILLINOIS, ASSIGNOB "1'0 ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y.', A CORPORATION 0] NEW You momma mirsnm.

Application filed April 17, 1928. Serial No. 102,7 28.

This invention relates to magnetic materials and magnet cores, and more especially to magnet cores for loadin coils fortelephone circuits, and their met 0d of production. I

The principal object of the invention is the production of a magnetic element having low losses and a relatively high permeabilit' to enable a given inductance to be d from a minimum amount of material and possessing to a high degree those electrical and ma netic characteristics which make it highly esirable in electrical signallin apparatus, particularly in loading coils or telephone circuits.

In accordance with one embodiment, the

present invention contemplates the construction of magnet cores of an allo including nigkg], and iro Tn finely divided form, heat treated to avea higher inherent magnetic ermeability and lower inherent hysteresis oss than iron and combined with a suitable I: u: More specifically, the on contemplates the formation of the IDS 1nvent1 jmagnet cores of a nickel iron allo in finely divided form in which the proportions of 1ts -constituents are more than 25% of nickel and the remainder principally iron, and in a form which has proven satisfactory, the nickel content being approximately 78 particles are dried and thoroughly mixed with day acid and a filler until they have receive a secondary insulating coating. The particles are then eated to 1ncrease the resistance of the final cores a ter which they are compressed into cores of the desired shape and size. The cores so formed are finally heat treated to the optimum temperature for t e par lcular alloy of which the cores are constructed to stabilize the in sulator and to give a high permeability and low hysteresis and eddy current losses.

It is believed that the invention will be clearly understood from the following detailed descri tion of one embodiment thereof and from t e accompanying drawing, in which 7 r Fig. I is a'perspectiveview of a section of a loading coil core made in accordance with, the; present invention, and

Fig. 2 shows a pluralit of these sections assembled to form a comp eted core. It Wlll be understood, however, that this 1s merely illustrative and the invention is not limited to the production of this form of core but is adapted to the production of cores of magnetic particles of many forms.

In carrying out the present invention, the magnetic material is prepared .in the following manner: The magnetic material employed is preferably prepared from a nickel iron alloy commonly referred to as ermal; lo which is treated in a manner ma e fdll y escribed in the copendin application of C. P. Beath and H. M. E. He1nicke, Serial No. 101,179, filed April 10, 1926, to reduce the alloy to a finely divided form. Experlence has proven that where low eddy current losses are desired it is essential that the particles be of small size and preferabl of such size that all ofthe particles wil readily pass through what is generallyj known as a 120 mesh screen and a. large percentage pass through a 200 mesh screen. According to one embodiment of theinvention, the alloy is prepared by melting approximately 78% parts of nickel and 21%' rocess the size of the crystalline structure 1s materially reduced, which since the disintegration of the material takes place mainly at the crystal boundaries, is essential in order to have a satisfacto yield of dust. The rolled slabs are broken 1nto short pieces and are then crushed in a jaw crusher, hammer mill, or any other suitable type of apparatus in which a further reduction occurs. The material after being passed through the jaw crusher is subsequently rolled in a ball mill until it is reduced to a fine dust. The dust is sieved through a 120 mesh sieve and any residue is remelted and the foregoing operation is repeated to a in reduce the material to a finely divided orm. Prior to the addition of the insulating material, the finely divided particles of the nickel I iron alloy are annealed in a closed container at a tem erature of approximatel 750 C. to 980 the temperature of a out 925 C. having proven to be one which produces very satisfactory results. It is then necessary to again reduced the annealed alloy which is now in the form of a cake to a finely divided form, after which it is mixed with the insulator.

According to one form of the invention, the insulator'for the primary coating of the dust particles is prepared by gredients in approximatel proportions: 1 arts of ry silicic acid to 1 part of water having approximately of base, Si 32.6%; Na O, 20.4%, sufiicient water to make a rather'dilute solution being added to the ingredients. This soluparticles added to'the solution, t e amoun of the permalloy particles added being de termined by the permeability desired and the particular use to which the finished cores are to be put. Theentire mass is then boiled t i al and magnetic standpoint.

By using an alloy of the proportions stated" in the preceding paragraphs and by fol-. lowing the foregoing method of insulating to dr ness accompanied by constant stirrin it?) prevelit caking and to insure a thorougl a primary coating of the individual dust particles', The dry coated particles are then placed in a revolving drum and d silicic aci and ferric oxide in the ratio 0 1 part 0 silicic aci 2 parts of ferric oxide are added to give the particles a secondary insulatin coating. T is mixture is tum bled in is e drum to thoroughly mix the in- I gredients until the dust particles assume a uniform red color which, since the ferric oxide is red, indicates that they are thoroughlypoated with'the secondary insulator. F0 lowing thisfstep thecoated dust particles 48 are placed in a furnace in which they are heated at the optimum annealing temperature 5? approximately Atjfii. in order to increase the resistanceof the finished rings, and c ooledg The dry insulated dust partiso cles lre'tfien in a form suitable for pressing into cores or rings which are preferably formed with a pressure of approximatel 200,000 pounds per square inch. A big pressure is used in forming the rings in order 6 to increase their density, since it has been found that the permeability of the rin increases with increased density. Final y the cores are transferred to an annealing furnace where they are a nealcd at a'temperature of from ggpfliCa. 0.

test rings'may be made of dust insulated in the above manner and their permeability measured.- Should their permeability be too 1 low, it maybe increased by the addition of is r a predetermined amount of uninsulated dust VI U55 HUI-UIUIIB'U tion is thoroughly mixed and-the permalloy' @C, A fewto the insulated dust before it is pressed into rings.

plurality of rings thus formed are stacked coaxially to form a core on which with a solution of water .glass and silicic acid in definite proportions and by tumbling them with silicic acid and ferric oxide in a definlikil ratilo, it is, of courfse,h to be igidersto t at t ie proportions o t e ingre ients mixiiig the in- V, the ollowing may be Jjli W1 oiit'departifigfromthe spirit and-scope of the invention. Also ther acids than silicic may be used with monic arsenous, arsenic, molybdic, tungstic, a o' "and lios home, an t e water glass'an erric oxi e"'may l1kewise be re- 'metasilicate suc as sTannic oxide,

the individual a loy particles and compressing the particles into cores or rings, magnet cores or rin s -are produced which have an extremely high permeability with a. minimum amount of material employed. By the use of such cores or rings, inductance units having the same permeability with equal or less hysteresis and eddy current losses as cores constructed according to previously known methods, but with much less core [.Xdiiii described as being insulated by coating them the following percentages of active silica and 5a is ac ory results, among these being anti- A placed with other alkalies such as sodium z. and sodium zincate, and fill man anese dioxide as" and on r1c"ox1de.and still roduce cores which are satisfactory from oth an elecios volume and-much less coil volume, are availa magnetic material, a primary insulatingv coating consisting of 1% parts of silicic acid and 1 part water glass, and a secondary insulating coating consisting of 1 part silicic acid and 1 parts of ferric oxide separating the particles. i

3. As a new article of manufacture," a magnetic substance composed of particles ofa magnetic material, and an insulating material consisting of an acid, an alkali, and a filler separating the'particles.

As anew article of manufacture, a

magnetic substance composed of finely divided particles of a magnetic alloy of nickel and iron, and an insulating material consisting of silicic acid, water glass, and a filler separating the particles.

5. As a new article of manufacture, a magnetic substance composed of finely divided particles of a magnetic alloy com-' posed of more than 25% nickel and the remainder principally iron, and an insulating material consisting of sil'icic acid, water glass, and ferric oxide separating the particles. g

'6. As a new article of manufacture, a magnetic substance composed of finely divided particles of a magnetic alloy composed of more than 25% nickel and the remainder principally iron,'and an insulating material consisting of 2 parts of silicic acid, 1 part of water glass, and 1 parts of ferric oxide separating the particles.

7. The method of making magnetic structures, which consists in coating particles of a magnetic material with an insulating material, consisting of an acid, an alkali and a filler, and forming a mass of such insulated particles into a homogeneous solid.

8. The'mcthodof making magnetic structures, which consists in coating particles of a magnetic material with an insulating material, consistin of silicic acid, water glass and fer-ric oxi e, and formin a mass of suplinsulated particles into a homogeneous so 1 9. The method of making magnetic structures composed of an alloy, which consists inreducing the alloy to finely divided. particles, heating the particles. again reducing the product so obtained to finely divided particles, coating the particles with an insulating material comprising silicic acid, water glass and ferric oxide, and forming a mass of such insulated particles into" a homogeneous solid.

10. The method of making magnetic structures composed 'of am alloy, which consists in reducing the alloy to finely divided particles, heating the particles, again reducing the product so obtained, to finely divided particles, coating the particles with an in-. sulating material comprising silicic acid, water glass and ferric oxide, heating the insulated particles, and forming a mass of sulcl:l insulated particles into a homogeneous so 1 11. The method of making magnetic structures composed of an alloy, which consists in reducing the alloy to finely divided particles, heating the particles, again reducing the product so obtained to finely divided particles, coating the particles with an insulating material comprising silieic acid, water glass and ferric oxide, heating the insulated particle's, forming a mass of such insulated heating the insulated particles, forming1 a mass ofsuch insulated particles into a 'mogeneous solid, and heating the solid mass to a hi h tem erature.

13. 'I he metiiod of making magnetic struc tures composed of an alloy vof more than 25% nickel and the remainder. principally iron, which consists in reducing the alloy to finely divided particles,heatin the particles and a ain reducing the'pro not so ob tained to nely divided particles, coatin the particles with an insulating materia comprising silicic acid, water gla'ssand ferric oxide, heating the insulated particles, forming a mass of vsuch insulated particles into a homogeneous solid, and heating tlfe solid mass to a high temperature.

14. The method of making magnetic structures, which consists in envelopin finely divided particles ofa nickel iron al loy with a primary coating of an insulating material consisting of silicic acid and water glass, enveloping thecoated particles with a secondary coating of an insulating material composed of silicic acid and ferric oxide, and forming a mas of such insulated particles into a homogeneous solid.

15. The method of making magnetic struc-- tures, which consists in enveloping finely divided particles of a ma etic alloy comprising more than 25% nickel and the remainder rincipally iron with a primary coating of an insulatin material consisting of 1 4. parts silicic acid and 1 glass, enveloping the coated particles with a secondany coating of an insulating material composed of 1 part silicic acid and 1 parts ferric oxide, heating the insulated particles comprising an acid and a filler.

In witness whereof, I hereunto subscribe my name this 31st day of March A. D., 1926.

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